This invention relates to a lockable valve having features which impede unauthorized removal of the valve from a conduit to which the valve is mounted.
Lockable valves have been known for more than ninety years prior to the present invention. Such valves include a housing defining a passageway, a valve element movably mounted to the housing and means for moving the valve element to selectively occlude the passageway. Locking means for arresting movement of the valve element are also known. Ordinarily, such arresting means have been operable to prevent movement of the valve element when such element is in a closed position, i.e., a position in which the valve element completely occludes the passageway. Such a valve is movably connected to a conduit, so that the passageway through the valve communicates with the interior of the conduit. When the valve element is in the open position fluid flows to or from the conduit through the valve passageway. When the valve element is moved to the closed position, it completely blocks flow through the passageway and hence to or from the conduit. Such lockable valves have been utilized to prevent unauthorized access to the fluid contained in a conduit. For example, lockable valves have been widely utilized in the gas utility industry on pipes leading from gas mains into buildings to prevent unauthorized use of gas.
A lockable valve having a rotatable valve element and arrest means including a lock concealed in the valve housing is described in U.S. Pat. No. 359,714, issued Mar. 22, 1887 to W. H. Deming, and another lockable valve having an internal lock is described in U.S. Pat. No. 2,016,797, issued Oct. 8, 1935 to F. S. Burns et al. A lockable valve having arrest means adapted simultaneously to connect the valve element and the housing to a removable lock which does not form part of the valve is illustrated in FIGS. 1 and 2 of U.S. Pat. No. 3,002,368, issued Oct. 3, 1961 to S. M. Moberg. Another valve which utilizes a removable lock is disclosed in U.S. Pat. No. 3,560,130, issued Feb. 2, 1971 to G. Horhota. As described in U.S. Pat. No. 4,024,740 issued May 24, 1977 to B. D. DiGiovanni, the arrest means of a lockable valve may consist of a hood adapted to conceal the stem or handle normally utilized to move the valve element. Each of these references describes a device for defeating attempts by unauthorized persons to move the valve element in the housing. None of them, however, addresses the problem of attempts to defeat the lock mechanism by unauthorized removal of the valve from the conduit. Even if the valve is perfectly secure against movement of the element in the housing by unauthorized persons, the lockable valve can readily be defeated by an unauthorized person if such person can readily remove the valve from the conduit.